Effect of anti-motion sickness drugs on motion sickness induced predisposition to hypothermia

Previous studies have shown that motion sickness (MS) potentiates the cooling rate of the body core. The aim of the present study was to investigate whether it is possible to influence this MS induced predisposition to hypothermia by administering two commonly used anti-MS drugs, namely the histaminereceptor blocker dimenydrinate (Amosyt®) and the muscarine-receptor blocker scopolamine (Scopoderm®). The effects of the drugs were investigated in 7 subjects in 5 experimental conditions during which each subject was immersed in 15 °C water (max 1.5 h) after administration of certain combinations of the two drugs and their respective placebo substances; in 4 of the conditions, the immersion was preceded by MS provocation. The results showed that MS potentiated the core cooling rate (? rectal temperature) and that this MS-induced predisposition to hypothermia was prevented by Amosyt® but not by Scopoderm®, which might suggest that the MS-induced predisposition to hypothermia is mediated via histaminergic rather than cholinergic neurons. The two active substances were similarly efficacious in ameliorating nausea suggesting that, during MS, no causal relationship exists between nausea and the predisposition to hypothermia.